The present invention relates to noncontact measurement of the width of the gap between a pair of rolls in a rolling mill.
Rolling mills usually require control of the gap for purposes of controlling the thickness of the stock. The width of the rolling gap is, for example, detected by electromechanical transducer means having two elements whose distance varies with the gap width and is ascertained by operation of the transducer. The dynamics of such a control poses a formidable problem, as it is, of course, desirable to adjust the roll gap as fast as possible. Thus, the gap width should be measured without any delay. Transducers for contactless measuring the gap width are comprised, for example, of inductive, capacitive or other systems. However, the inductive systems are apparently more widely used and are preferred over the others. U.S. Pat. No. 3,662,576 discloses, for example, such a system for measuring the absolute value of the gap. The U.S. Pat. No. 3,817,008 discloses equipment for a relative measurement of gap width.
Both of these known systems have been practiced with advantage particularly because they operate with little sensitivity against temperature variations. It was found, however, that the employment of rings as part of the sensing equipment is not always possible. For example, they were not found practical for fast mills, and their life in a hot rolling mill was somewhat limited.